cell biology

• Eukaryotes


  Animals and plants
• Animal cell


  • Nucleus (controls cell activities, contains DNA for protein synthesis)
  • Cytoplasm (where chemical reactions take place)
  • Cell membrane (controls what goes in and out, partially permeable)
• Plant cell


  • Nucleus (controls cell activities, contains DNA for protein synthesis)
  • Cytoplasm (where chemical reactions take place)
  • Cell membrane (controls what goes in and out, partially permeable)
  • Cell wall (for strength and support, made of cellulose)
  • Sap vacuole (contains cell sap, a sugary solution)
  • Chloroplast (contains chlorophyll to absorb sunlight for photosynthesis)
• Prokaryotes


  Usually bacterial cells, have no nucleus or subcellular structures with membranes
• Approximate sizes: Animal cell 10 micrometers, Plant cell 50 micrometers, Prokaryote 5 micrometers
• Cell differentiation


  1. Undifferentiated cells (e.g. sperm and egg) can differentiate into specialized cells (e.g. nerve, muscle, sperm)

  2. In animals, specialized cells usually only divide for repair and replacement

  3. In plants, many cells can still differentiate into other plant cell types
• Nerve cell


  • Cell body with cytoplasm
  • Dendrites (connect to other nerve cells)
  • Axon (long projection that carries impulses)
  • Insulating sheath to speed up electrical impulses
  • Axon terminals/synapses
• Sperm cell


  • Mid piece with mitochondria (provide energy for tail)
  • Tail (for swimming towards egg)
  • Acrosome (contains enzymes to penetrate egg cell membrane)
  • Nucleus (contains 23 chromosomes)
• Muscle cell


  • Fibers that can shorten for contraction
  • Mitochondria (provide energy for contraction)
  • Glycogen (stored energy)
• Xylem cell


  • Long tube-shaped, no end plates, no cytoplasm (dead tissue)
  • Rings of lignin (woody material to support and prevent collapse)
• Phloem cell


  • Long tube-shaped, little cytoplasm, have end plates with pores
  • Companion cells (provide energy for sugar transport)
• Root hair cell


  • Large surface area, many mitochondria (for active transport of water and minerals)
• Microscopes


  • Simple microscopes have low magnification and low resolving power
  • Electron microscopes have high magnification and high resolving power, enabling more subcellular structures to be seen
• Units of size


  • Millimeters (1/1000 of a meter)
  • Micrometers (1/1000 of a millimeter)
  • Nanometers (1/1000 of a micrometer)
• Magnification


  Size of image / Size of real object
• Culturing microorganisms


  1. Bacteria divide by binary fission, doubling every 20 minutes

  2. Sterilize equipment, inoculate agar plate, incubate at 25°C, seal to prevent contamination

  3. Test antibiotics/antiseptics by measuring zones of inhibition around discs
• Cell cycle


  1. Stage 1: Cell growth and DNA replication

  2. Stage 2 (Mitosis): Chromosomes line up, then separate to opposite ends of cell

  3. Stage 3: Cytoplasm and cell membrane divide to form two genetically identical cells
• Stem cells


  • Embryonic stem cells are undifferentiated and can differentiate into any cell type
  • Adult stem cells can only differentiate into certain cell types
• Cell growth and division

  1. Cell grows and increases number of subcellular structures

  2. DNA replicates to form two copies of each chromosome

  3. Chromosomes line up along center and are pulled to each end of cell

  4. Cytoplasm and cell membranes divide to form two genetically identical cells
• Mitosis


  The process of cell division described above
• Embryonic stem cells


  Undifferentiated cells from the fertilized egg that can differentiate into most other cell types
• Adult stem cells


  Stem cells found in tissues like bone marrow that can differentiate into various cell types
• Plant stem cells


  Found in meristem tissue in root and shoot tips, can differentiate into any plant cell
• Therapeutic cloning


  1. Patient body cell nucleus inserted into enucleated human egg cell

  2. Cloned cells can be differentiated to produce specialized cells/tissues for treatment

  3. Avoids rejection by patient
• Diffusion


  The spreading out of particles in a solution or gas, resulting in net movement from higher to lower concentration
• Factors affecting rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area
• Active transport


  Movement of particles from lower to higher concentration, requires energy
• Surface area to volume ratio

  Ratio of surface area to volume, decreases as organism size increases
• Adaptations for exchange in larger organisms

  • Villi and microvilli in small intestine
  • Alveoli in lungs
  • Stomata in leaves
  • Gill filaments in fish
• Osmosis


  Diffusion of water from dilute to concentrated solution through a partially permeable membrane
• Investigating effect of solutions on plant tissue mass

  1. Prepare solutions of different concentrations

  2. Cut equal-sized plant tissue samples

  3. Immerse samples in solutions

  4. Measure mass change after time
• Potato loses mass


  Solution outside is more concentrated than inside, so water moves out by osmosis
• Potato gains mass


  Solution inside is more concentrated than outside, so water moves in by osmosis